Pars plana vitrectomy is a closed vitreous surgical technique for operating on the eye wherein the surgical field is observed through the pupil and instrumentation is inserted into the vitreous cavity through surgical cuts or sclerotomies which are fitted with ports to prevent leakage of intraocular fluid. Visualization is accomplished using a viewing system, such as a binocular indirect opthalmomicroscope system described in U.S. Pat. No. 4,710,000 or 5,009,487. Intraocular pressure is regulated by infusion of fluid through a separate sclerotomy port. Illumination of the back of the eye or fundus may be originated from an external source through the pupil, or internally through fiber optics. It has been generally recognized that internal illumination with fiber optics is superior to external illumination and is not as dependent on variances in pupillary dilatation or clarity of the ocular media. A frequent practice is to employ a three- or four-port procedure, utilizing one or two ports for exchangeable working instruments, another port for infusion, and another port for illumination using a source such as a ceiling light available from D.O.R.C. Company, Geervleit, The Netherlands, or a chandelier system available from Grieshaber, Schafthausen, Switzerland.
It is known to incorporate optical fibers into the working end of the surgical instrument. This eliminates the need for a separate illumination port and offers the advantage of directing the light beam together with the instrument onto the target site. Instrument sizes must, however, be correspondingly increased and larger sclerotomies may be necessary. An alternative procedure is to employ an illuminated infusion cannula to integrate the infusion and illumination functions at a single point.
One example of a combined infusion cannula and illumination source is given in U.S. Pat. No. 4,820,264. The '264 device comprises an infusion channel through which light transmitting fibers are passed for directing light into the eyeball at the point of discharge of the intraocular irrigating solution. Such illumination is not automatically directed by manipulation of the cutting instruments. Moreover, the fibers are run directly within the infusion channel, and illumination and infusion portions are non-separable near the eye.
The integrated lighting concept has been extended to provide illuminated cannulas at multiple ports having channels through which either infusion fluids or surgical instruments can be passed. Such a multiport illuminated cannula system is described in Koch, et al. "The Retinal Irradiance and Spectral Properties of the Multiport Illumination System for Vitreous Surgery" appearing at 116 Am. J. Ophthalmology 489-496 (October 1993) and is the subject of Koch's copending application U.S. Ser. No. 07/750,114, entitled "Illuminated Leading Probe Device and Method," the disclosures of both of which are incorporated herein by reference. Such multiport illuminated cannula comprises a plurality of light transmitting fibers annularly arranged about a central instrument-receiving working channel. Such device has the advantage that fibers are located external to the working channel. The channels are, however, awkward to seal upon instrument removal and, if used for infusion purposes, lack expedient infusion tube interfaces and, as in the '264 device, discharge fluid directly at the optical fiber terminations, thereby interfering with illumination.